Conventional coil components include a coil component described in WO 01/036904 A1. The coil component is used for a thickness detection apparatus detecting a thickness of a paper sheet such as paper money. The coil component is disposed on a portion of a printed circuit board making up a circuit of a detection apparatus.
A roller for detecting a thickness of a paper sheet as a displacement amount is disposed to face the coil component and a high-frequency magnetic field is generated from the coil component to detect an eddy-current loss caused by bringing the coil component closer to the roller. As a result, a displacement amount of a roller is detected to detect the thickness of the paper sheet.